Clean up #included files in src/include directories (#1518)

[jrgemignani]

Cleaned up #included files in the .h files in the src/include directories.

Additionally, deleted 1 unnecessary header file.

modified:   src/include/catalog/ag_catalog.h
modified:   src/include/catalog/ag_graph.h
modified:   src/include/catalog/ag_label.h
modified:   src/include/catalog/ag_namespace.h
modified:   src/include/commands/graph_commands.h
modified:   src/include/commands/label_commands.h
modified:   src/include/executor/cypher_executor.h
modified:   src/include/executor/cypher_utils.h
modified:   src/include/nodes/ag_nodes.h
modified:   src/include/nodes/cypher_copyfuncs.h
modified:   src/include/nodes/cypher_nodes.h
modified:   src/include/nodes/cypher_outfuncs.h
modified:   src/include/nodes/cypher_readfuncs.h
modified:   src/include/optimizer/cypher_createplan.h
modified:   src/include/optimizer/cypher_pathnode.h
modified:   src/include/parser/cypher_clause.h
modified:   src/include/parser/cypher_expr.h
modified:   src/include/parser/cypher_gram.h
modified:   src/include/parser/cypher_item.h
modified:   src/include/parser/cypher_parse_node.h
modified:   src/include/parser/cypher_parser.h
modified:   src/include/parser/cypher_transform_entity.h
modified:   src/include/utils/ag_cache.h
modified:   src/include/utils/ag_float8_supp.h
modified:   src/include/utils/ag_func.h
modified:   src/include/utils/age_global_graph.h
modified:   src/include/utils/agtype.h
modified:   src/include/utils/agtype_parser.h
modified:   src/include/utils/agtype_raw.h
modified:   src/include/utils/graphid.h
modified:   src/include/utils/load/ag_load_edges.h
modified:   src/include/utils/load/ag_load_labels.h
modified:   src/include/utils/load/age_load.h

deleted:    src/include/utils/ag_load.h

[dehowef]

All checks passed, looks good to me.